1. Field of the Invention
The disclosures herein generally relate to a plasma processing apparatus and a particle adhesion preventing method.
2. Description of the Related Art
In a process chamber in which a plasma process is performed on a semiconductor wafer (hereinafter, simply referred to as a “wafer”), while the plasma process is being performed, reaction products are generated or substances constituting an inner wall of the process chamber are removed by plasma. Those products or substances formed into particles and adhering to the wafer might lead to a defect in a semiconductor device formed on the wafer, thereby reducing the yield ratio. Hence, Japanese Laid-Open Patent Application Publication No. 2013-102237 proposes a method for preventing the particles from adhering to the wafer. In Japanese Laid-Open Patent Application Publication No. 2013-102237, as soon as a dry-etching process is completed, a supply of direct-current power to an upper electrode is stopped. After a given period of time elapses, supplies of radio-frequency power for plasma generation and radio-frequency power for bias voltage generation are stopped.
According to Japanese Laid-Open Patent Application Publication No. 2013-102237, however, at the time of stopping the supply of direct-current power, sheath potential might fluctuate drastically and the particles might adhere to the wafer.